KR100221163B1 - Apparatus and method for optimizing the quality of a received signal in a radio receiver - Google PatentsApparatus and method for optimizing the quality of a received signal in a radio receiver Download PDF
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- KR100221163B1 KR100221163B1 KR1019960019514A KR19960019514A KR100221163B1 KR 100221163 B1 KR100221163 B1 KR 100221163B1 KR 1019960019514 A KR1019960019514 A KR 1019960019514A KR 19960019514 A KR19960019514 A KR 19960019514A KR 100221163 B1 KR100221163 B1 KR 100221163B1
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- 239000000047 products Substances 0 description 7
- 230000035945 sensitivity Effects 0 description 7
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- 230000001702 transmitter Effects 0 description 6
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- 230000002452 interceptive Effects 0 description 4
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- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04W—WIRELESS COMMUNICATION NETWORKS
- H04W52/00—Power management, e.g. TPC [Transmission Power Control], power saving or power classes
- H04W52/18—TPC being performed according to specific parameters
FIG. 1 is an overall block diagram of a wireless transceiver according to the present invention; FIG.
Figure 2 is a detailed block diagram of a wireless receiver in a wireless transceiver of Figure 1 according to the present invention.
FIG. 3 is a graph showing the RF power of a desired radio frequency (RF) power, the thermal noise power for gain, the interference power for gain, the sum of thermal noise power and interference power for gain, .
4 is an alternative detailed block diagram of a gain controller in a wireless transceiver of FIG. 1 according to the present invention; FIG.
DESCRIPTION OF THE REFERENCE NUMERALS
100: wireless transceiver 102: wireless transmitter
104: wireless receiver 106: antenna
114: Signal processor 204: Variable attenuator
220, 272, 276, and 293:
The present invention relates generally to wireless receivers, and more particularly, to an apparatus and method for optimizing the quality of a signal received at a wireless receiver.
An example of a wireless transceiver that provides an environment suitable for explaining the need of the present invention is a cellular radiotelephone mobile subscriber unit. A wireless subscriber unit is typically designed to operate in a dual cellular system (e.g., system A or B) that provides competitive services in a particular geographic area. Each system is assigned a number of channels with a particular channel spacing, each of which is described, for example, by Electronic Industries Association TIA / EIA / IS-95, (As referred to as the " IS-95 standard ") of the Mobile Station Land Station Compatibility Standard for a Modular Broadband Expansion Spectrum Cellular System Frequency.
A commercial subscriber unit is designed to operate on an A system or a B system. Therefore, the subscriber unit simultaneously receives all radio frequency (RF) signals within the cellular reception band provided at any given time and location. This includes both the A and B system signals. The receiver converts the RF signal so that the desired signal is centered in the passband of an intermediate frequency (IF) filter that passes the desired signal and attenuates the unwanted signal. The IF filter does not infinitely attenuate unwanted signals, so some unwanted signals pass through the IF filter at a reduced level. In addition, undesired signals interact with each other at the receiver through a process known as intermodulation to generate new interference signals at the same frequency of the desired signal. Intermodulation will be described in detail below. This problem is exacerbated as the ratio of the level of the unwanted RF signal to the level of the desired RF signal increases. A and B system designers attempt to minimize the occurrence of the above problems through system design, but it is difficult to completely solve the above problems.
Especially, I will explain about situations that are difficult to overcome. If the mobile subscriber is operating in the A channel, i.e., receiving the desired RF signal from the A system base station to the A system channel, the desired RF signal level decreases as the mobile subscriber moves away from the A base station. At the same time, the mobile subscriber moves towards the B system base station, which transmits multiple RF signals to the B system channel. The signal is an unwanted RF signal to the mobile subscriber operating in the A system. As the mobile subscriber approaches the B system base station, the level of the unwanted RF signal increases. Therefore, an undesirable situation occurs in which the desired RF signal level is reduced and the unwanted RF signal level is increased. If the ratio of the level of the unwanted RF signal to the level of the desired RF signal becomes too high, then the user of the mobile subscriber unit will have experience such as poor call quality or no service.
With reference to the above problems, reference is made to a CDMA mobile station operating in a code division multiple access (CDMA) wireless system which is a digital system and a sdvanced mobile telephone system (AMPS) I will explain. The mobile station communicates with the desired base station during the call operation. The wireless receiver of the mobile station detects a decrease in the ratio of Ec / Io that can be caused by an unwanted strong signal. Ec is the energy perchip of the desired signal and Io is the total power spectral density of the desired signal. The mobile station's radio receiver informs the communicating base station of the fact that the Ec / Io ratio is decreasing. The base station then increases the energy per chip (Ec) of the desired signal to improve the strength of the desired signal at the radio receiver. However, increasing the energy per chip (Ec) of the desired signal decreases the overall capacity of the wireless system. Also, the energy per chip (Ec) of the desired signal can be increased to any limit. Even at the maximum energy per chip (Ec) of the desired signal, unwanted signals can overwhelm the desired signal. Such a situation occurs when the mobile station is very close to the base station transmitting the undesired signal, and when it is far from or blocked from the base station transmitting the desired signal. Therefore, the ratio of Ec / Io decreases. As the bill rate of Ec / Io decreases, the frame error rate (FER) of the mobile station of the received signal increases and eventually the active call is interrupted.
Quot; intermodulation distortion " (IM)). ≪ / RTI > The IM distortion develops when there are two or more interfering signals that are spaced apart from the assigned input signal frequency, which has the same frequency as the input signal frequency assigned by the N-th order mixing of two or more interfering signals occurring in the non- A third signal is generated which is referred to as an IM distortion product. The transfer function of an electronic device conventionally used in amplification and mixing circuits is rarely completely linear. The non-ideal characteristics inherent in such a device cause IM distortion.
For example, the well-known form of IM distortion is the third-order IM distortion. If the signal strength of the interfering signal fluctuates by 1 dB, the signal strength of the unwanted third order IM distortion product varies by 3 dB. To understand the background of this 3: 1 relationship, a paper submitted by Richard C. Sagers of Motorola Inc. at the 32nd IEEE Automotive Technology Conference, May 23-25, 1982 &Quot; Intercept points and unwanted responses " can be referred to. The 3: 1 relation described above is commonly used in the receiver design in order to eliminate the third-order IM distortion as much as possible.
It is also known that increasing the bias current of an electronic device at a receiver generally helps to reduce IM distortion. However, the portable wireless subscriber unit obtains power from the portable power source. The portable wireless subscriber unit is designed to minimize power consumption so that it can be used in a low current-standby mode when waiting for a call or in a high-current-user operating mode in which voice or data is transmitted and received. Therefore, it is not desirable to increase the current consumption of the receiver to reduce the IM distortion because increasing the current consumption reduces the time available for the portable wireless unit.
System design is also known to reduce IM distortion. Such as using a directional antenna at a base station, etc. may be included in the system design. The distance between the base station and the radio receiver is an important factor in the level of the signal received at the radio receiver. Thus, placing an unwanted base station that transmits an unwanted signal that causes IM distortion common to the desired base station that transmitted the desired signal significantly reduces the likelihood that the IM distortion will overwhelm the desired signal. However, common placement of base stations of different systems is not always possible due to factors such as, for example, the physical location of the base station, the time lapse between base station installations, ownership of the base station,
If the base station has a directional antenna, the signal transmitted by the directional antenna helps to reduce the IM distortion since it has increased power in the desired direction through the short-directional antenna. Increasing the signal power increases the likelihood that the desired signal will not be overwhelmed by the IM distortion. However, the reduction in IM interference is due to the relative distance between the desired base station with directional antenna and the radio receiver, which undesirably causes IM distortion. Therefore, the orientation of the antenna from the desired base station may not overcome the IM distortion if the radio receiver is very close to the undesired base station and away from the desired base station. Directional antennas also sacrifice signal reach in the other direction and limit the wireless reach of the system, so more base stations are needed to increase wireless reach.
Mobile radio devices, such as cellular telephones, must be able to operate over channels with dynamically changing conditions, including thermal noise, interference. Thermal noise is set by receiver noise characteristics, receiver bandwidth, temperature, and so on. Thermal noise changes relatively slowly under most conditions. On the other hand, interference is caused by various factors and mechanisms, and changes at a relatively high speed. Factors of interference include common-channel interference, loss of adjacent channel sensitivity, and intermodulation (IM).
Receiver designers typically refer to stages in the receiver configuration that are closest to the antenna as the receiver front end and those that are far from the antenna as the receiver back end. Typically, the potential gain of the receiver is set high enough to recover the worst-case receiver back-end noise characteristics to reach acceptable sensitivity.
Typically, the first active stage in a receiver configuration is a low noise amplifier (LNA) with a fixed gain. The gain of the LNA is set high to minimize receiver noise characteristics and to achieve acceptable receiver sensitivity. However, the weakness of high LNA gain is in linearity. If you increase the LNA gain, then the stage following the LNA, such as a down mixer, should be made more linear to maintain the same IM performance. The greater the linearity, the greater the DC power consumption, which is obviously undesirable for battery-operated wireless devices. Conversely, lowering the LNA gain to improve IM performance degrades receiver sensitivity. Therefore, there is a trade-off between sensitivity, IM rejection, and receiver DC power consumption in conventional wireless devices.
The problem of achieving acceptable reciprocity between sensitivity, IM rejection, and receiver DC power consumption is specifically required for CDMA radio devices rather than AMPS cellular radio devices because: First, the CDMA channel is 40 times wider than the AMPS channel, and the on-channel IM generation products are more likely to occur. Second, the CDMA IF filter loss is 10 to 20 dB greater than the AMPS IF filter loss. Therefore, the potential gain must be greater to compensate for the back-off noise characteristics and to achieve equal sensitivity. Both of these characteristics of conventional CDMA radio equipment will increase receiver potential DC power consumption to a constant of 5 to 6 compared to AMPS radio equipment for proper linearity and maintenance of IM rejection.
In order to reduce receiver power consumption while reducing the level of interference, a wireless receiver that dynamically increases its linearity characteristics in the presence of interference is desirable. Accordingly, there is a need for an apparatus and method for optimizing the quality of a signal received at a wireless receiver.
Hereinafter, the present invention will be described in detail with reference to the drawings. FIG. 1 is an overall block diagram of a wireless transceiver 100 in accordance with the present invention. The wireless transceiver 100 generally includes a wireless transmitter 102, a wireless receiver 104, and an antenna 106. The wireless transmitter 102 transmits information via the antenna 106 and the wireless receiver 104 receives information via the antenna 106.
In a preferred embodiment of the present invention, the wireless transceiver 100 is a cellular radiotelephone subscriber unit. The wireless transceiver 100 may have various forms known in the art, such as a vehicle-mounted, portable, or portable unit. According to a preferred embodiment of the present invention, the mobile station is a CDMA mobile station designed for a CDMA cellular radiotelephone system as described in the aforementioned IS-95 standard.
Generally, the wireless transceiver 100 and the antenna 106 are well known in the art and will not be described in more detail, unless necessary to understand the present invention. Wireless transmitter 102 is in accordance with Motorola cordless telephone model number SUF1712, which is generally referred to herein. The wireless transmitter 102 receives information at the information input 120. The information is typically voice or data.
The wireless receiver 104 is novel and will generally be described with reference to Figure 1 and will be described in more detail with reference to Figures 2 to 4. The wireless receiver 104 generally includes a receiver 108 having a gain and a demodulator 110, a signal quality determiner 111, a gain controller 112, and a signal processor 114. The wireless transmitter 102 generates information at the information output terminal 116. The information is typically voice or data. Generally, since the gain receiver 108, demodulator 110, signal quality determiner 111, gain controller 112, and signal processor 114 are well known in the art, I will not explain it in any detail except for. The beneficial receiver 108 is in accordance with the Motorola cordless telephone model number SUF1712 and U.S. Pat. No. 5,321,847, which are generally incorporated herein by reference. Demodulator 110 and signal quality determiner 111 are generally referred to in the " CDMA Mobile Station Modem ASIC ", Proceedings of the IEEE 1992 Integrated Circuits Conference, section 10.2, pages 1 to 5) (ASIC) as described in " CDMA Digital Cellular System ASIC Overview ", Proceedings of the IEEE 1992 < RTI ID = 0.0 & do. The signal processor 114 generally includes, for example, a channel decoder, error detection / correction unit, audio processor, data processor, as known in the art.
Generally, the wireless receiver 104 of the present invention receives a desired RF signal modulated by a first modulation method, but also receives an interfering RF signal that is sometimes modulated by a second modulation method. The two methods of modulating the RF signal include analog modulation and digital modulation. Modulated RF signals using analog modulation techniques are referred to as digital RF signals, and modulated RF signals using digital modulation techniques are referred to as digital RF signals. A wireless transceiver capable of receiving and transmitting an analog radio frequency (RF) signal or a digital RF signal is known as a dual mode wireless transceiver. In a preferred embodiment of the present invention, the radio receiver 104 may receive an analog RF signal or a code division multiple access (CDMA) RF signal. Dual mode repair receivers capable of receiving analog or CDMA RF signals are known in the art and are generally described in the aforementioned IS-95 standard. Alternatively, the present invention may be used in time division multiple access (TDMA) radio receivers and Group Special Mobile (GSM) radio receivers. Dual mode receivers capable of receiving analog or TDMA RF signals are known in the art and generally conform to the Motorola cordless telephone model number SUF1702C referred to herein. Wireless receivers capable of receiving GSM RF signals are also known in the art and generally conform to the Motorola cordless telephone model number SUF1702C referred to herein.
The gain controller 112 is coupled to a gain receiver 108, a demodulator 110, a signal quality determiner 111 and a signal processor 114 to provide a novel apparatus and method, And will be described in detail with reference to FIGS. 2 to 4. Generally, the apparatus and method within the wireless receiver 104 is to optimize the quality 130 of the received signal 124 at the wireless receiver 104 with the gain. The present invention is useful for any wireless receiver capable of determining the quality of the received signal 124. In particular, a gain receiver 108 receives a radio frequency (RF) signal 122 and generates a received signal 124. The signal quality determiner 111 determines the quality 130 of the received signal 124. The gain controller 112 adjusts the gain of the wireless receiver 104 in response to the quality 130 of the received signal 124.
The signal processor 114 also processes the demodulated signal 126 to generate a processed signal 128 at the information output stage 116.
In a preferred embodiment of the present invention, the gain controller 112 is implemented in software. Alternatively, the gain controller 112 may be implemented as a separate part or in an integrated circuit.
The gain controller 112 may be designed to adjust the gain of the wireless receiver 104 in any analogy suitable for the wireless receiver 104. [ In addition, the gain controller 112 may be designed to adjust the gain of the wireless receiver 104 either incrementally or continuously, respectively, depending on whether the implementation is digital or analog. The gain controller 112 is preferably operable when the quality 130 of the received signal falls below a predetermined threshold but the gain controller 112 may also be operable when the wireless receiver 104 is in service have.
In a preferred embodiment of the present invention, the RF signal 122 has a receive frequency band ranging from 869 MHz to 894 MHz. In an embodiment of the present invention, the received signal 124 includes a desired signal and an unwanted signal. The unwanted signals include, for example, noise that occurs within the receiver and distortion products that occur within the receiver, including IM distortion products. In a preferred embodiment of the present invention, the quality 130 of the received signal 124 is characterized by the ratio of the desired signal to the received signal 124. In a CDMA system the ratio is characterized by the energy per chip (Ec) of the desired signal relative to the total power spectral intensity (Io) of the received signal.
The quality 130 of the received signal 124 may be derived from various signal points of the wireless receiver 104. Alternatively, the signal quality determiner 111 may determine the error rate of the demodulated signal 126 or the processed signal 128 (as shown by the dashed line to the signal quality determiner 111) An error rate calculator may be provided. The error rate derived from the demodulated signal 126 is the symbol error rate. The gain controller 112 adjusts the gain of the wireless receiver 104 in response to the symbol error rate of the demodulated signal 126. The error rate derived from the processed signal 128 is the bit error rate. The gain controller 112 adjusts the gain of the wireless receiver 104 in response to the bit error rate of the processed signal 128. All such signal points for deriving the quality 130 of the received signal 124 generate virtually the same type of information for the gain controller 112. The specific signal points for deriving the quality 130 of the received signal 124 are in accordance with the modulation method, radio receiver topology and other known design conditions.
FIG. 2 is a detailed block diagram of a wireless receiver 104 of FIG. 1 according to the present invention. In general, the receiver 108 and gain controller 112 are shown in more detail in FIG. The receiver 108 generally includes a first bandpass filter 202, a variable attenuator 204, a variable gain amplifier 206, a second bandpass filter 208, a mixer 210, a local oscillator 212, Band pass filter 214, an intermediate frequency (IF) stage 216, a received signal strength indication (RSSI) estimator 217, and an RSSI compensator 218. The RSSI compensator 218 includes a summer 220 and a delay element 222. In general, a first band pass filter 202, a variable attenuator 204, a variable gain amplifier 206, a second band pass filter 208, a mixer 210, a local oscillator 212, The intermediate frequency (IF) stage 216, the RSSI calculator 217, the summer 220 and the delay element 222 are well known in the art and thus are not necessary to understand the present invention I will not explain it in more detail.
The first band pass filter 202 filters the RF signal 122 to generate a first filtered signal 224. The variable attenuator 204 attenuates the first filtered signal in response to the first gain control signal 132 to generate the attenuated signal 228. The variable gain amplifier 206 amplifies the attenuated signal 228 in response to the second gain control signal 133 from the gain controller 112 to generate the amplified signal 232. The term " amplification " generally refers to varying the level of the attenuated signal 228 and includes both increasing and decreasing the level of the attenuated signal 228. Alternatively, the variable gain amplifier 206 may be implemented as a fixed gain amplifier (not shown) followed by a variable gain attenuator (not shown) as is known. Alternatively, the gain control signal from gain controller 112 may cause the gain of other known elements of wireless receiver 104 to vary. The second band pass filter 208 filters the amplified signal 232 to generate a second filtered signal 234. [ The mixer 210 mixes the second filtered signal 234 in response to the local oscillator signal 236 generated in the local oscillator 212 to generate an IF signal 238. The third bandpass filter 214 filters the IF signal 238 to generate a filtered IF signal 240. The intermediate frequency (IF) stage 216 receives the filtered IF signal 240 and generates a received signal 124. The RSSI applicator 217 calculates the RSSI of the filtered IF signal 240. The receiver configuration including the first band pass filter 202 to the IF stage 216 (202, 204, 206, 208, 210, 212, 214, 216, 217) is conventional and will not be described in further detail.
The RF signal 122 includes a desired RF signal and an unwanted RF signal. An unwanted RF signal includes one or more RF signals centered at various RF frequencies. The wireless receiver 104 requires RSSI estimation of the desired RF signal for various reasons known in the wireless receiver design arts. The RSSI estimate of the desired RF signal provided by the RSSI estimator is a function of the total gain before the RSSI estimate. Therefore, if the gain of the variable gain amplifier 206 fluctuates, the RSSI estimate value 242 does not display the RSSI of the desired RF signal well. The RSSI estimate of the desired RF signal provided by the RSSI estimator is a function of the total gain of the RSSI estimator. Therefore, in an embodiment of the present invention, the RSSI compensator 218 compensates the RSSI estimate 242 in response to the gain of the silent receiver 104 and compensates for the received signal 124 indicative of the RSSI of the desired RF signal 122 Gt; RSSI 134 < / RTI > The RSSI compensator 218 is implemented with a summer 220 and a delay element 222. The summer 220 sums the RSSI of the received signal 242 and the delayed gain signal 244 and subtracts the limited gain control signal 246 to generate the compensated RSSI 134 of the received signal 124. Therefore, no gain is imposed on the received signal 124 to obtain an appropriate estimate of the RSSI of the received signal 242. [
The gain controller 112 generates a limited gain control signal 246 in response to the quality 130 of the received signal 124 and adjusts the gain of the wireless receiver 104 in response to the limited gain control signal 246.
In a preferred embodiment of the present invention the gain controller 112 includes a first comparator 248, a second comparator 250, a gain control signal determiner 252, a first delay element 254, a second delay element 256 ). In general, since the first comparator 248, the second comparator 250, the gain control signal determiner 252, the first delay element 254, and the second delay element 256 are well known in the art, I will not elaborate on the details except when necessary to understand the invention. The first comparator 248 compares the current measurement of the quality 130 of the received signal 124 at the positive input 258 of the first comparator 248 to the received signal 124 at the negative input 260 of the first comparator 248 And produces a first output signal 262 that is estimated to be a value of +1 or -1 as compared to the current measurement of the quality 130 of the signal 124. [ The second comparator 250 compares the current measurement of the gain 246 at the positive input 264 of the second comparator 250 with the past measurement of the gain 246 at the negative input 266 of the second comparator 250 To produce a second output signal 268 that is estimated to be a value of +1 or -1. The gain control signal determiner 252 determines the gain control signal 270 in response to the first and second output signals 262 and 268.
The gain control signal determiner 252 includes a first multiplier 272, a second multiplier 274, a summer 276, and a delay element 284. The gain control signal determiner 252 includes a first multiplier 272, a second multiplier 274, a summer 276, In general, the first multiplier 272, the second multiplier 274, the summer 276, and the delay element 284 are well known and will not be described in more detail unless necessary to understand the present invention. The first multiplier 272 multiplies the first output signal 262 by the second output signal 268 to produce a multiplied signal 278. The second multiplier 274 multiplies the multiplied signal 278 by a predetermined gain control step value dG to generate a gain control step signal 280. [ A summer 276 sums the gain control step signal 280 with the past gain control signal 282 provided by the delay element 284 to generate the current gain control signal 270.
In a preferred embodiment of the present invention the gain controller 112 includes a limiter 286 that limits the gain control signal 270 between a maximum value 288 and a minimum value 290 to produce a limited gain control signal 246 And further comprising: In the second figure, for purposes of illustration, the value of the gain control signal 246 is equal to the desired net gain of the attenuator 204 and VGA 206. In general, limiter 286 is well known and will not be described in more detail, unless necessary for understanding the present invention.
In a preferred embodiment of the present invention, the limiter 286 of the gain controller 112 limits the gain control signal 270 to a maximum value 288 in response to the compensated RSSI 134. If the received signal is strong, limiting the maximum gain can minimize the initial impact of the instantaneous IM burst.
In a preferred embodiment of the present invention, the gain controller further comprises a switch 294. The switch 294 is characterized in that it includes a first summer 293, a second summer 295, a first limiter 296 and a second limiter 297. The first summer output 298 is generated by subtracting the VGA control signal 133 from the limited control signal 246. [ The first summing output 298 is limited to a maximum value 291 by a first limiter 296 and generates an attenuator control signal 132. And subtracts the attenuator control signal 132 from the limited control signal 246 to generate a second summer output 299. The second summer output 299 is limited to a minimum value 292 by the second limiter 297 and generates the attenuator control signal 133. [ In general, the first summer 293, the second summer 295, the first limiter 296, and the second limiter 297 are well known, and therefore will be described in more detail except when necessary to understand the present invention I will not.
The gain of the VGA 206 fluctuates in response to the gain control signal 133 when the gain control signal 246 is set so that the second summer output is greater than the minimum value 292. [ At this time, the attenuator 204 is suppressed to a minimum attenuation. The attenuation value of the attenuator 204 varies in response to the gain control signal 132 when the gain control signal 246 is set such that the first summer output 298 is less than the maximum value 291. [ At this time, the gain of the VGA 206 is suppressed to the minimum allowable VGA gain. In an alternative embodiment, only the attenuator 204 or only the VGA 206 may be varied.
The integration period of the signal quality determiner 111, which determines Ec / Io, determines the minimum repetition period for the gain adjustment loop. The minimum integration time is 64 chips and corresponds to approximately 50 microseconds. If automatic gain control (AGC) and active filtering are implemented at the back end of the receiver, it is necessary to consider the timing so that the signal can be within the instantaneous dynamic range of the posterior. To stabilize the posterior AGC, the integration period must be increased or the number of consecutive gain steps in the same direction in a given time period must be limited.
Another advantage of having a gain adjustment at the front end of the wireless receiver 104 is that the dynamic range of the wireless receiver extends. The IF section 216 of the wireless receiver 104 is typically a first stage for saturating with a strong signal. Therefore, the dynamic range of the wireless receiver 104 is extended through potential gain reduction.
Figure 3 shows a graphical representation of the receiver thermal noise power (N) 306 associated with the input of the receiver, the interference power (I) 307 associated with the input of the receiver, the receiver thermal noise power associated with the input of the receiver, The desired RF signal power 310 at the receiver input to the net gain 301 of the attenuator 204 and the VGA 206, and the like. The receiver thermal power associated with the input of the receiver is reduced as the receiver potential gain increases. In Figure 3, the interference power associated with the input of the receiver is believed to be due to the IM distortion occurring in the receiver due to the unwanted RF signal received at the receiver. Thus, the sum 308 of receiver thermal noise power related to the input of the receiver is increased as the receiver potential gain increases. Therefore, the sum 308 of the receiver thermal noise power associated with the input of the receiver has a minimum value A 316 at the value 314 of the numerical gain G. [ The desired RF signal power is independent of the receiver potential gain since it is a function of external factors such as the distance from the transmitting source. Thus, the apparatus and method of the present invention adjusts the localization gain to a gain 314 that maximizes the ratio of the desired RF signal power to the sum of the receiver thermal noise associated with the receiver input and the interference power associated with the input of the receiver. The above-mentioned maximum ratio corresponds to the optimal received signal quality.
In FIG. 3, receiver thermal noise and IM interference are considered to be the main factors of signal quality degradation. If a factor of side distortion or noise, such as signal distortion due to the saturation characteristic of the stage following the potential, is inherent in the receiver, the present invention adjusts to a gain value that minimizes the sum of the distortion products along all potential gains, To maximize the quality of the product.
Gim 314 provides an initialized starting point for the net gain for the gain control loop. At this point, the ratio 315 of Ior / (N + I) is a predetermined minimum value, for example, -1.1 dB. In a preferred embodiment of the present invention, the gain controller 112 dynamically adjusts the receiver gain based on the signal-to-noise ratio (Ec / Io) of the wireless receiver 104. When multiple rake fingers are used in a CDMA wireless receiver, the largest Ec / Io available from the Rake finger is used. The basic operation of the gain controller 112 includes two steps. First, if the current value of Ec / Io is better than the previous Ec / Io value, the gain controller 112 advances the gain in the same direction as the previous gain step. Second, if the current value of Ec / Io is worse than the previous Ec / Io value, the gain controller 112 advances the gain in the opposite direction to the previous gain step. The gain of VGA 206 varies for each new Ec / Io sample. If the loop is stable to the optimal gain environment G (314), the gain toggles up and down in the optimal environment.
FIG. 4 is a detailed block diagram of an alternative embodiment of the gain controller 112 of FIG. 1 according to the present invention. In general, the alternative gain controller 400 is characterized by including a first comparator 402, a second comparator 404, and an AND gate 406. In general, the first comparator 402, the second comparator 404, and the AND gate 406 are well known in the art, and will not be described here unless necessary to understand the present invention. The first comparator 402 determines whether the quality 130 of the received signal is good or bad. In an embodiment of the present invention, the quality is Ec / Io as described above. The determination process consists of comparing the determined Ec / Io with a pre-selected Ec / Io lease value 410 to generate a first output signal 414. In a preferred embodiment of the present invention, the RSSI 134 of the received signal is the compensated RSSI 134 as described above. The determination process consists of comparing the compensated RSSI 134 with a pre-selected RSSI threshold 408 to generate a second output signal 412. The predetermined RSSI threshold value 408 sets the attenuator 204 not to be switched on the basis of the selected attenuator value at a received signal level where the ratio of Ior / N is reduced to a predetermined ratio or less. I or is the desired RF signal power from the desired base station and N is the thermal noise of the receiver relative to the receiver input. The alternative gain controller 400 adjusts the gain of the wireless receiver 104 when both the quality 130 of the received signal 124 and the RSSI 134 are good. A good decision is made when both the first output signal 414 and the second output signal 412 are at a logic high at the input of the AND gate 406 because the RSSI 134 rises and Ec / Occurs when a decrease in ratio 130 is detected. The alternative gain controller 400 may determine that the quality 130 of the received signal 124 or the RSSI 134 is bad or the quality 130 of the received signal 124 and the RSSI 134 are both bad, ). ≪ / RTI > A good determination is made when either the first output signal 414 and the second output signal 412, or one of them, is at a logic low level at the input of the AND gate 406.
Accordingly, the present invention provides an apparatus and method for optimizing the quality of a signal received at a wireless receiver. The present invention has the advantage of reducing mutual distortion at the wireless receiver. This advantage is substantially provided by the novel gain controller 112 that adjusts the gain of the wireless receiver 104 in response to the quality 130 of the signal 124 being received. According to the present invention, the problem of the prior art in which a telephone call is disconnected when an undesired strong RF signal is received is almost solved.
While the invention has been described with reference to illustrative embodiments, it is not intended that the invention be limited to such specific embodiments. It will be understood by those skilled in the art that modifications and variations can be made in the present invention without departing from the spirit or scope of the invention as set forth in the claims.
- A method of optimizing the quality (130) of a received signal in a wireless receiver (104) having a gain, the method comprising: receiving a radio frequency (RF) signal (122) to generate a received signal (124) Determining a quality 130 of the received signal 124; evaluating a received signal strength indication (RSSI) of the received signal 124; Determining whether the RSSI of the received signal 124 is good or bad and determining whether the quality of the received signal 124 is good or unfavorable; Adjusting the gain of the wireless receiver 104 in response to the quality 130 of the received signal 124 if both of the RSSIs of the signal 124 are good; 124 is bad or the quality of the received signal 124 is poor And not adjusting the gain of the wireless receiver (104) if the RSSI of the received signal (124) is bad.
- The method of claim 1, wherein the received signal comprises a desired signal and an undesired signal, and the quality of the received signal is determined by a ratio of a desired signal to the received signal, Wherein the ratio is expressed as energy per chip (Ec) of a desired signal with respect to the total power spectral density (Io) of the received signal.
- The method of claim 1, wherein the RF signal comprises a desired RF signal and an undesired RF signal, the method further comprising compensating RSSI (242) of the received signal (124) in response to a gain of the wireless receiver Generating a compensated RSSI (134) of the received signal (124) indicative of RSSI of a desired RF signal.
- 2. The method of claim 1, further comprising generating a gain control signal (132, 133) in response to a quality (130) of the received signal (124) Wherein the quality of the received signal is optimized.
- 5. The method of claim 4, wherein generating comprises comparing a current measured value (258) of the quality (130) of the received signal (124) with a past measured value (260) of the quality And generating a second output signal 268 by comparing the current measured value 264 of the gain 246 with a past measured value 266 of the gain 246 And determining (252) the gain control signal (270) in response to the first output signal (262) and the second output signal (268).
- 6. The method of claim 5, wherein the determining comprises multiplying the first output signal (262) by the second output signal (268) to produce a multiplied signal (278) Multiplying the gain control step signal 280 by the control step value dG and summing the gain control step signal 280 with the current gain control signal 282 to obtain a gain control signal 270 Wherein the method further comprises the steps of:
- 5. The method of claim 4, further comprising limiting the gain control signal (270) between a maximum value (288) and a minimum value (290).
- An apparatus for optimizing the quality of a received signal in a wireless receiver having a gain, the apparatus comprising: a receiver for receiving a radio frequency (RF) signal and generating a received signal; a signal quality determiner for determining a quality of the received signal; A first comparator for determining whether the quality of the received signal is good or bad and a second comparator for determining whether the RSSI of the received signal is good or bad, And a controller for adjusting the gain of the wireless receiver in response to the quality of the received signal if both the quality of the received signal and the RSSI of the received signal are good and the quality of the received signal and the RSSI of the received signal If the quality of the received signal is bad or the RSSI of the received signal is both bad, a gain that does not adjust the gain of the wireless receiver ≪ / RTI > wherein the controller is configured to optimize the quality of the received signal at the wireless receiver.
Priority Applications (3)
|Application Number||Priority Date||Filing Date||Title|
|Publication Number||Publication Date|
|KR970004390A KR970004390A (en)||1997-01-29|
|KR100221163B1 true KR100221163B1 (en)||1999-09-15|
Family Applications (1)
|Application Number||Title||Priority Date||Filing Date|
|KR1019960019514A KR100221163B1 (en)||1995-06-02||1996-06-01||Apparatus and method for optimizing the quality of a received signal in a radio receiver|
Country Status (6)
|US (1)||US5758271A (en)|
|JP (1)||JP3989572B2 (en)|
|KR (1)||KR100221163B1 (en)|
|CN (1)||CN1080954C (en)|
|AR (1)||AR002163A1 (en)|
|CA (1)||CA2175860C (en)|
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Also Published As
|Publication number||Publication date|
|US5722061A (en)||Method and apparatus for increasing receiver immunity to interference|
|US6038435A (en)||Variable step-size AGC|
|US5265119A (en)||Method and apparatus for controlling transmission power in a CDMA cellular mobile telephone system|
|KR100959230B1 (en)||Automatic gain control for a wireless receiver|
|US6670901B2 (en)||Dynamic range on demand receiver and method of varying same|
|AU754973B2 (en)||Programmable linear receiver|
|EP1309093B1 (en)||Method and apparatus for reducing the effect of AGC switching transients|
|EP1513268B1 (en)||Method and apparatus for increasing receiver immunity to interference|
|US8243864B2 (en)||Noise reduction filtering in a wireless communication system|
|RU2158474C2 (en)||Linearized digital automatic gain control|
|RU2212093C2 (en)||Automatic gain control circuit for controlling a number of adjustable-gain amplifier stages in generating estimate of received signal power|
|CA2120768C (en)||Transmitter power control system|
|US5737687A (en)||Self-attenuating RF transceiver system using antenna and modem interfaces and cable link|
|US6661832B1 (en)||System and method for providing an accurate estimation of received signal interference for use in wireless communications systems|
|US5485486A (en)||Method and apparatus for controlling transmission power in a CDMA cellular mobile telephone system|
|US7522885B2 (en)||Method and apparatus for continuously controlling the dynamic range from an analog-to-digital converter|
|US5469471A (en)||Method and apparatus for providing a communication link quality indication|
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|US7280811B2 (en)||Multimode wireless terminal and wireless transmitter-receiver unit|
|EP0855111B1 (en)||Apparatus and method for controlling the actual transmission power of a base station in a cellular communications system|
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